>>> On 4/5/2010 at 5:36 PM, in message < 4BBA57FB.2000406@xxxxxxxx >, Jeremy
Fitzhardinge < jeremy@xxxxxxxx > wrote:
> On 04/05/2010 01:30 PM, Ky Srinivasan wrote:
>> +static cycle_t read_hv_clock(struct clocksource *arg)
>> +{
>> + cycle_t current_tick;
>> + /*
>> + * Read the partition counter to get the current tick count. This count
>> + * is set to 0 when the partition is created and is incremented in
>> + * 100 nanosecond units.
>> + */
>> + rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
>> + return current_tick;
>> +}
>> +
>> +static struct clocksource clocksource_hyperv = {
>> + .name = "hyperv_clocksource",
>>
>
> Seems like a redundantly long name; any use of this string is going to
> be in a context where it is obviously a clocksource. How about just
> "hyperv"
>
>> + .rating = 400, /* use this when running on Hyperv*/
>> + .read = read_hv_clock,
>> + .mask = CLOCKSOURCE_MASK(64),
>> + .shift = HV_CLOCK_SHIFT,
>> +};
>> +
>> +static struct dmi_system_id __initconst
>> +hv_timesource_dmi_table[] __maybe_unused = {
>> + {
>> + .ident = "Hyper-V",
>> + .matches = {
>> + DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
>> + DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
>> + DMI_MATCH(DMI_BOARD_NAME, "Virtual Machine"),
>> + },
>> + },
>> + { },
>> +};
>> +MODULE_DEVICE_TABLE(dmi, hv_timesource_dmi_table);
>>
>
> So you use the DMI signatures to determine whether the module is needed,
> but cpuid to work out if the feature is present?
>
>> +
>> +static struct pci_device_id __initconst
>> +hv_timesource_pci_table[] __maybe_unused = {
>> + { PCI_DEVICE(0x1414, 0x5353) }, /* VGA compatible controller */
>> + { 0 }
>> +};
>> +MODULE_DEVICE_TABLE(pci, hv_timesource_pci_table);
>>
>
> And/or PCI?
>
> Seems a bit... ad-hoc? Is this the official way to determine the
> presence of Hyper-V?
The presence of HyperV and our ability to use the partition-wide counter obviously is checked via probing the cpuid leaves. The DMI/PCI signatures are used in auto-loading these modules.
>
>> +
>> +
>> +static int __init hv_detect_hyperv(void)
>>
>
> This looks generally useful. Should it be hidden away in the
> clocksource driver, or in some common hyper-v code? Do other hyper-v
> drivers have versions of this?
Good point. Right now, I can think of multiple drivers replicating this code. We could include hyperV detection code in cpu/hypervisor.c . I will spin up a patch for doing that shortly.
>
>> +{
>> + u32 eax, ebx, ecx, edx;
>> + static char hyp_signature[20];
>>
> 20? static?
>
>> +
>> + cpuid(1,&eax,&ebx,&ecx,&edx);
>> + if (!(ecx& HV_HYPERVISOR_PRESENT_BIT)) {
>> + printk(KERN_WARNING
>> + "Not on a Hypervisor\n");
>>
> This just looks like noise, especially since it doesn't identify what is
> generating the message. And if you compile this code in as =y
> (non-modular) then it will complain every boot.
>
>> + return 1;
>> + }
>> + cpuid(HV_CPUID_SIGNATURE,&eax,&ebx,&ecx,&edx);
>> + *(u32 *)(hyp_signature + 0) = ebx;
>> + *(u32 *)(hyp_signature + 4) = ecx;
>> + *(u32 *)(hyp_signature + 8) = edx;
>> + hyp_signature[12] = 0;
>> +
>> + if ((eax< HV_CPUID_MIN) || (strcmp("Microsoft Hv", hyp_signature))) {
>>
>
> memcmp, surely?
>
>> + printk(KERN_WARNING
>> + "Not on HyperV; signature %s, eax %x\n",
>> + hyp_signature, eax);
>> + return 1;
>> + }
>> + /*
>> + * Extract the features, recommendations etc.
>> + */
>> + cpuid(HV_CPUID_FEATURES,&eax,&ebx,&ecx,&edx);
>> + if (!(eax& 0x10)) {
>> + printk(KERN_WARNING "HyperV Time Ref Counter not available!\n");
>> + return 1;
>> + }
>> +
>> + cpuid(HV_CPUID_RECOMMENDATIONS,&eax,&ebx,&ecx,&edx);
>> + printk(KERN_INFO "HyperV recommendations: %x\n", eax);
>> + printk(KERN_INFO "HyperV spin count: %x\n", ebx);
>> + return 0;
>> +}
>> +
>> +
>> +static int __init init_hv_clocksource(void)
>> +{
>> + if (hv_detect_hyperv())
>> + return -ENODEV;
>> + /*
>> + * The time ref counter in HyperV is in 100ns units.
>> + * The definition of mult is:
>> + * mult/2^shift = ns/cyc = 100
>> + * mult = (100<< shift)
>> + */
>> + clocksource_hyperv.mult = (100<< HV_CLOCK_SHIFT);
>>
>
> Why not initialize this in the structure? It's just 100<<22 isn't it?
>
>> + printk(KERN_INFO "Registering HyperV clock source\n");
>> + return clocksource_register(&clocksource_hyperv);
>> +}
>> +
>> +module_init(init_hv_clocksource);
>> +MODULE_DESCRIPTION("HyperV based clocksource");
>> +MODULE_AUTHOR("K. Y. Srinivasan< ksrinivasan@xxxxxxxxxx >");
>> +MODULE_LICENSE("GPL");
>> Index: linux/drivers/staging/hv/Makefile
>> ===================================================================
>> --- linux.orig/drivers/staging/hv/Makefile 2010-04-05 13:02:06.000000000 -0600
>> +++ linux/drivers/staging/hv/Makefile 2010-04-05 13:02:13.000000000 -0600
>> @@ -1,4 +1,4 @@
>> -obj-$(CONFIG_HYPERV) += hv_vmbus.o
>> +obj-$(CONFIG_HYPERV) += hv_vmbus.o hv_timesource.o
>> obj-$(CONFIG_HYPERV_STORAGE) += hv_storvsc.o
>> obj-$(CONFIG_HYPERV_BLOCK) += hv_blkvsc.o
>> obj-$(CONFIG_HYPERV_NET) += hv_netvsc.o
>>
Jeremy, thank you for your comments. I am attaching the next version of this patch that addresses the comments I have gotten thus far.
Regards,
K. Y
From: K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>
Subject: A clocksource for Linux guests hosted on HyperV.
References: None
Patch-mainline:
This patch is a clocksource implementation suitable for guests hosted on HyperV.
Time keeping in Linux guests hosted on HyperV is unstable. This clocksource
driver fixes the problem.
Signed-off-by: K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>
Index: linux/drivers/staging/hv/hv_timesource.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/staging/hv/hv_timesource.c 2010-04-07 12:17:29.000000000 -0600
@@ -0,0 +1,147 @@
+/*
+ * A clocksource for Linux running on HyperV.
+ *
+ *
+ * Copyright (C) 2010, Novell, Inc.
+ * Author : K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <linux/version.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/dmi.h>
+
+#define HV_CLOCK_SHIFT 22
+/*
+ * HyperV defined synthetic CPUID leaves:
+ */
+#define HV_CPUID_SIGNATURE 0x40000000
+#define HV_CPUID_MIN 0x40000005
+#define HV_HYPERVISOR_PRESENT_BIT 0x80000000
+#define HV_CPUID_FEATURES 0x40000003
+#define HV_CPUID_RECOMMENDATIONS 0x40000004
+
+/*
+ * HyperV defined synthetic MSRs
+ */
+
+#define HV_X64_MSR_TIME_REF_COUNT 0x40000020
+
+
+static cycle_t read_hv_clock(struct clocksource *arg)
+{
+ cycle_t current_tick;
+ /*
+ * Read the partition counter to get the current tick count. This count
+ * is set to 0 when the partition is created and is incremented in
+ * 100 nanosecond units.
+ */
+ rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+ return current_tick;
+}
+
+static struct clocksource hyperv_cs = {
+ .name = "hyperv_clocksource",
+ .rating = 400, /* use this when running on Hyperv*/
+ .read = read_hv_clock,
+ .mask = CLOCKSOURCE_MASK(64),
+ /*
+ * The time ref counter in HyperV is in 100ns units.
+ * The definition of mult is:
+ * mult/2^shift = ns/cyc = 100
+ * mult = (100 << shift)
+ */
+ .mult = (100 << HV_CLOCK_SHIFT),
+ .shift = HV_CLOCK_SHIFT,
+};
+
+static const struct dmi_system_id __initconst
+hv_timesource_dmi_table[] __maybe_unused = {
+ {
+ .ident = "Hyper-V",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
+ DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
+ DMI_MATCH(DMI_BOARD_NAME, "Virtual Machine"),
+ },
+ },
+ { },
+};
+MODULE_DEVICE_TABLE(dmi, hv_timesource_dmi_table);
+
+static const struct pci_device_id __initconst
+hv_timesource_pci_table[] __maybe_unused = {
+ { PCI_DEVICE(0x1414, 0x5353) }, /* VGA compatible controller */
+ { 0 }
+};
+MODULE_DEVICE_TABLE(pci, hv_timesource_pci_table);
+
+
+static int __init hv_detect_hyperv(void)
+{
+ u32 eax, ebx, ecx, edx;
+ char hyp_signature[20];
+
+ cpuid(1, &eax, &ebx, &ecx, &edx);
+
+ if (!(ecx & HV_HYPERVISOR_PRESENT_BIT))
+ return 1;
+
+ cpuid(HV_CPUID_SIGNATURE, &eax, &ebx, &ecx, &edx);
+ *(u32 *)(hyp_signature + 0) = ebx;
+ *(u32 *)(hyp_signature + 4) = ecx;
+ *(u32 *)(hyp_signature + 8) = edx;
+
+ if ((eax < HV_CPUID_MIN) ||
+ (memcmp("Microsoft Hv", hyp_signature, 12))) {
+ printk(KERN_WARNING
+ "Not on HyperV; signature %s, eax %x\n",
+ hyp_signature, eax);
+ return 1;
+ }
+ /*
+ * Extract the features, recommendations etc.
+ */
+ cpuid(HV_CPUID_FEATURES, &eax, &ebx, &ecx, &edx);
+ if (!(eax & 0x10)) {
+ printk(KERN_WARNING "HyperV Time Ref Counter not available!\n");
+ return 1;
+ }
+
+ cpuid(HV_CPUID_RECOMMENDATIONS, &eax, &ebx, &ecx, &edx);
+ printk(KERN_INFO "HyperV recommendations: %x\n", eax);
+ printk(KERN_INFO "HyperV spin count: %x\n", ebx);
+ return 0;
+}
+
+
+static int __init init_hv_clocksource(void)
+{
+ if (hv_detect_hyperv())
+ return -ENODEV;
+ printk(KERN_INFO "Registering HyperV clock source\n");
+ return clocksource_register(&hyperv_cs);
+}
+
+module_init(init_hv_clocksource);
+MODULE_DESCRIPTION("HyperV based clocksource");
+MODULE_AUTHOR("K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>");
+MODULE_LICENSE("GPL");
Index: linux/drivers/staging/hv/Makefile
===================================================================
--- linux.orig/drivers/staging/hv/Makefile 2010-04-07 12:17:25.000000000 -0600
+++ linux/drivers/staging/hv/Makefile 2010-04-07 12:17:29.000000000 -0600
@@ -1,4 +1,4 @@
-obj-$(CONFIG_HYPERV) += hv_vmbus.o
+obj-$(CONFIG_HYPERV) += hv_vmbus.o hv_timesource.o
obj-$(CONFIG_HYPERV_STORAGE) += hv_storvsc.o
obj-$(CONFIG_HYPERV_BLOCK) += hv_blkvsc.o
obj-$(CONFIG_HYPERV_NET) += hv_netvsc.o
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